1. Field of the Invention
The invention relates to a method for the production of a soft magnetic core for generators and generator with a core of this type. For this purpose, plurality of laminations of a soft magnetic alloy magnetically activatable by a final annealing process is stacked and the stack is given the shape of a soft magnetic core, e.g., by eroding the core assembly. The final shaping of the core assembly is usually followed by final annealing to optimise the magnetic properties of the core in its final form.
2. Description of Related Art
A method of this type for the production of a core in the form of a stack of a plurality of thin-walled layers of a magnetically conductive material is known from CH 668 331 A5. In this known method, the cold rolled soft magnetic laminations for the individual layers are stacked in identical orientation and eroded to form the final core. The erosion process may be followed by the final annealing of the core consisting of a plurality of thin-walled layers of a magnetically conductive material.
In such a process, however, there is a risk that the dimensions of the core may be changed by this final annealing or formatting, in particular if there is an anisotropic rearrangement of the soft magnetic core at certain phase formations during the final annealing or activation process, which affects large-volume soft magnetic cores in particular, as these are more prone to anisotropic dimensional changes. Such anisotropic changes may in addition cause unbalance in rotating core structures, which leads to significant problems in high-speed machines, in particular in aviation applications.
The cold rolling process moreover results in a crystalline texture, which may cause anisotropies of magnetic and mechanical properties. These anisotropies are undesirable in rotating cores, such as those of a high-speed rotor or of stators interacting with rotating components, because such applications demand a precisely rotationally symmetrical distribution of magnetic and mechanical properties.
The teaching of CH 668 331 A5, wherein cold rolled laminations are evenly stacked in rolling direction in order to utilise the increased magnetic effect in the direction of the “GOSS texture” for stationary magnetic heads, can therefore not be applied to the requirements of rotating cores. There is therefore a need for developing new manufacturing solutions to meet the demand for a rotationally symmetrical uniformity of the magnetic and mechanical properties of a soft magnetic core in generators.